Ultrafast decay dynamics of water molecules excited to electronic D&cmb.tilde;′ and D&cmb.tilde;′′ states: a time-resolved photoelectron spectroscopy study

The ultrafast decay dynamics of water molecules excited to D&cmb.tilde;′ 1 B 1 and D&cmb.tilde;′′ 1 A 2 states is studied by combining two-photon excitation and time-resolved photoelectron imaging methods. The lifetime of the D&cmb.tilde;′ 1 B 1 (000) state of H 2 O (D 2 O) is determined to be 1.54 ± 0.1 (22.6 ± 1.6) ps, consistent with a previous high-resolution spectroscopic study. The H 2 O D&cmb.tilde;′′ 1 A 2 (000) state decays with a lifetime of 4.1 ± 0.2 ps, while in the D 2 O D&cmb.tilde;′′ 1 A 2 (000) state, two independent decay pathways are observed, with time constants of 0.55 ± 0.1 and 13 ± 1 ps, respectively. The former is proposed to be associated with a hitherto undocumented D&cmb.tilde;′′ → C&cmb.tilde; pathway, induced by Coriolis interaction. The ultrafast decay dynamics of water molecules excited to D&cmb.tilde;′ and D&cmb.tilde;′′ states is studied in detail.